Thyroid Disorders in Pregnancy


The optimum production and circulation of thyroid hormones is very crucial for the normal growth and development of the fetus and mother’s wellbeing as it regulates the cellular metabolism.

To ensure the adequate supply of these hormones, the size, blood supply and function of thyroid gland increases under the influence of Estrogen and Human Chorionic Gonadotropin hormones.

In the first trimester, the fetus is entirely dependent for all its hormonal requirements on mother. After 14 weeks onwards, it sufficiently produces its own hormones. However, it still depends on mother for the supply of raw materials like Iodine and Proteins.

Normal values of Thyroid Stimulating hormone (TSH) in Pregnancy:

Anterior Pituitary hormone produces Thyroid stimulating hormone that regulates the function of thyroid gland and subsequently the production of thyroid hormones.

The decreased functioning of thyroid gland or increased demand of hormone results in positive feedback to anterior pituitary resulting in high levels of Serum TSH, whereas, the hyperfunctioning of thyroid gland and high levels of thyroid gland gives negative feedback and suppress TSH levels.


Hypothyroidism in Pregnancy:

It affects around 5-10% of mothers in pregnancy.

It happens either because of the increased metabolic demand of pregnancy or because of the dysfunction of thyroid gland. Whatever the reason of hypothyroidism, the anterior pituitary gland produces more Thyroid Stimulating Hormone (TSH) to stimulate the thyroid gland to produce more hormones. Hence, in hypothyroidism, the level of TSH rises above normal values (0.3 – 3 IU/L) to maintain euthyroidism.

Symptoms of Hypothyroidism in Pregnancy:

The common symptoms of hypothyroidism in Pregnancy are central obesity, history of irregular menstrual cycle preconception, difficulty in conception, depression, anxiety, mood swings, hair fall, dry skin, swelling in lower limbs, high blood pressure, diabetes, high cholesterol levels etc.


Side effects of Hypothyroidism on Mother:

  • Miscarriage.
  • Preterm labor.
  • Pregnancy induced hypertension.
  • Gestational diabetes.
  • Recurrent vulvo-vaginitis.
  • Post delivery hemorrhage.
  • Maternal anemia.

Side effects of Hypothyroidism on Baby:


Causes of Hypothyroidism:

  • Deficiency of raw material like Iodine or Protein synthesis.
  • Dysfunction of thyroid gland.
  • Thyroid gland destruction by autoimmume antibodies.
  • Previous radiation injury to thyroid gland.
  • Exposure to harmful substances, drugs or viral infections that damage thyroid gland.

Management of Hypothyroidism:

The treatment of hypothyroidism, irrespective of reason, is to replace the active thyroid hormone (Levothyroxin or T3) to target the normal TSH values in blood between 0.3 to 3 IU/L.

The dose of levothyroxine may fluctuate during pregnancy and post delivery.

Due to misconception that they may become dependent on medicine life long, many mothers avoid taking medicine and unknowingly complicate the pregnancy and harm the baby.

Hyperthyroidism in Pregnancy:

It affects around 0.5 % pregnant mothers.

The hyperactive thyoid glands produces excess thyroid hormones leading to abnormal high levels of free T3 and free T4 hormones subsequently resulting in lower production of Thyroid Stimulating Hormone due to negative feedback by anterior pituitary and its lower level in blood .

Symptoms of Hyperthyroidism in Pregnancy:hyperthyroidism-in-pregnancy_0

The common symptoms of hyperthyroidism are weight loss, malaise, weakness, anxiety, palpitations, breathlessness, tremors, excessive vomiting, excessive sweating, warm extremities, irritable bowel, insomnia etc. Some mothers may have protruding scary eyes.

Side effects of Hypothyroidism on Mother:

  • Miscarriage.
  • Preterm labor.
  • Pregnancy induced hypertension.
  • Gestational diabetes.
  • Post delivery hemorrhage.
  • Maternal anemia.
  • Congestive heart failure.
  • Separation of placenta from its bed.
  • Thyroid storm or crisis, which is a life threatening condition.

Side effects of Hypothyroidism on Fetus:

  • Intrauterine growth retardation.
  • Intrauterine fetal death.
  • Prematurity.

Causes of Hyperthyroidism:

  • Stimulating Autoimmune Antibodies.
  • Inflammation or infection of thyroid glands.
  • Drugs and substances that stimulate thyroid function.
  • Multifetal pregnancy.
  • Placental overproduction of HCG hormone.
  • Molar pregnancy, where the baby degenerates into a mass of grape like structure.

Management of Hyperthyroidism:

The treatment of hyperthyroidism, irrespective of reason, is to suppress the thyroid hormone production with the help of medicines to target the normal TSH values in blood between 0.3 to 3 IU/L.

The three medicines that are often used are Propylthiouracil, Carbimazole and Methimazole. These three interrupts the process of Iodinisation of Tyrosine protein and control thyroid hormone production. These medicine are notorious to cause teratogenecity when used in first trimester and hence needs proper counseling and informed consent. They can also adversely affect the mother causing skin problems, itching, vomiting, fever and bone marrow suppression leading to anemia and agranulocytosis.

According to certains studies, the preferred medicine with least side effects is Propylthiouracil.

According to World Health Organisation and other International organisations, all the pregnant mothers should be offered universal screening with Serum TSH to access the thyroid function to ensure the safety of mother and fetus.



The information is shared to create awareness towards Pregnancy and Childcare to reduce maternal and child deaths. Atmost care has been taken by the author to include the verified information from authentic sources. However, kindly discuss the same with your health care provider before implementation.